A half-duplex system provides for communication in both directions, but only one direction at a time (not simultaneously). Typically, once a party begins receiving a signal, it must wait for the transmitter to stop transmitting, before replying. In automatically-run communications systems, such as two-way data-links, the time allocations for communications in a half-duplex system may be controlled by the hardware. Thus, there is no waste of the channel for switching. For example, one user equipment (UE) on one end of the wireless link could be allowed to transmit for one second, and then another UE on the other end could be allowed to transmit for one second.
It is not uncommon that new generation of user equipment supports multiple radio stacks that may be activated simultaneously to support multiple services on different radio technologies. A radio stack may include radio specific hardware and protocol software to enable the user equipment to operate on a particular frequency. Multiple radio stacks operating on frequencies related in a certain way may create intermodulation interference to each other.